The present invention relates to a range measuring method-and device, more particularly to a technique in which the light beam for measuring the distance of a target extends along the same optical axis as the aiming sight of an observer.
There are two major existing techniques employing light beam with constant wavelength for measuring a distance between a target and an observer. One utilizes multiple invisible light beams with different transmission angles to calculate the distance between the target and the measurer according to the contained angle or the distance between the transmitters. In the other technique, the invisible light beam is transmitted from the transmitter to the target and reflected back to the receiver beside the transmitter. The distance between the target and the measurer is calculated according to the time difference between the transmission and receiving of the light beam.
In practical, the second measuring technique is applied to a laser range finder. Such a laser range finder mainly includes an invisible light beam transmitter, a receiver and a telescope for the measurer to aim at and identify the target and the measured section thereof.
In the general laser range finder, a winding traveling path of the invisible light beam is formed between the transmitter and the receiver, while the telescope has another observation line between the eyes of the observer and the target. (That is, a traveling path of visible light beam.) The visible and invisible light beams travel respectively along independent paths. Therefore, the laser range finder employing such measure has two shortcomings as follows:
1. The volume is larger. The laser transmitter, laser receiver and telescope each has a considerable length and diameter. In addition, several lenses must be respectively disposed thereon. As a result, the combination of the three components will lead to a large volume of the laser range finder.
2. The precision is relatively poor. In use of the laser range finder, an advancing path and a returning path of the invisible light beam are produced between the laser transmitter, laser receiver and the target. Also, an advancing path of the visible light beam is produced between the telescope and the target. The respective paths are spaced from each other by a certain distance and the angles contained thereby vary with the different distances of the targets. Therefore, even though an electronic circuit is used in cooperation with the laser range finder to calculate the distance in accordance with complicated formulas, the measurement result is still not very accurate.
Although the above three independent light beam paths can be combined to a certain extent to improve the aforesaid shortcomings, to the existent knowledge, once any two of the three paths are combined, it will immediately take place that the path of the invisible light beam for measurement or the path of the visible light beam for observation is blocked. Under such circumstance, the function of range finding or observation will be lost.
It is therefore a primary object of the present invention to provide an measuring method and a device whose the volume is effectively reduced.
It is a further object of the present invention to provide an measuring method and device having better measurement precision.
It is still a further object of the present invention to provide an measuring method and device in which the traveling paths of the light beam for measurement and the light beam for observation extend along the same straight line without affecting the measurement and aiming of a user.
According to the above objects, the measuring method and device of the present invention serves to provide a traveling path of light beam. The traveling path includes a front portion between a target and a prism unit, a refraction portion entering the prism unit and extending inside the prism unit and a first and a second rear portions positioned outside the prism unit and corresponding to the front portion. A visible light beam and an invisible light beam simultaneously travel along the front portion. The visible light beam enters the prism unit and is reflected and then emerges from the prism unit. Thereafter, the visible light beam travels along the first rear portion which is positioned on the same line as the front portion. The invisible light beam enters the prism unit in a predetermined direction and is reflected and then emerges from the prism unit. Thereafter, the invisible light beam travels along the front portion or the second rear portion. The second rear portion contains a predetermined angle respectively with the front portion and the first rear portion. Therefore, very long parts of the traveling paths of the visible light beam and the invisible light beam coincide with each other and are commonly directed to a specific portion of the target. Accordingly, a better measurement precision can be achieved and the volume of the device can be reduced without affecting the measuring function.
The present invention can be best understood through the following description and accompanying drawings wherein: